There has been conventionally proposed an oscillation circuit having a function of periodically changing an oscillation frequency of a clock signal so as to suppress a noise due to the clock signal (a so-called frequency spreading function).
However, for example, when this proposed oscillation circuit is used as a clock signal source of an emission driver with a pulse width modulation (PWM) dimming function, there are concerns that an output current supplied to a light source is greatly varied due to the influence of frequency spreading, which may result in a flicker.